Toward Measuring Prompt Fission Products in Coincidence

Despite the discovery of fission nearly 80 years ago and its importance to nuclear energy, national security, and astrophysics, there are very few measurements of the correlations between multiple fission products. An experiment is underway at Oak Ridge National Laboratory to measure the energy and angle correlations between prompt fission neutrons, γ rays, and fragments. These measurements could reveal the existence of scission neutrons, the energy balance between these products, and other details needed for benchmarking advanced fission models. The setup includes an array of VANDLE neutron detectors and a γ-ray detector positioned opposite a suite of detectors to determine the mass of one fragment. Preliminary results with a spontaneous ²⁵²Cf source show expected correlations between prompt fragments and neutrons along the fission axis. Further refinements will improve the resolution of the fragment mass and increase efficiency for triple-coincident events. Future experiments could be done with a neutron beam to study induced fission on thin targets.